A highly accurate compound-eye unit is provided, which can assemble a compound-eye lens member to a lens holder with high positional accuracy even when using the compound-eye lens member that is unsatisfactory in dimensional accuracy of an external shape. A highly accurate compound-eye unit is provided, which can assemble a light shielding member having a plurality of apertures with high positional accuracy. A distance W2 between centers of apertures AP2, AP3 is smaller than a distance W1 between optical axes of convex lens units PL2, PL3, and hence, as illustrated in FIG. 13, when a lens member IM3 is made to approach a lens holder LH along an optical-axis direction, optical surfaces or external portions of peripheral surfaces of convex lens units PL2, PL3 abut on edge portions of the apertures AP2, AP3 at two points P, Q, and a flat surface FP abuts on an abutting portion CT. At this time, the flat surface FP abuts on the abutting portion CT, whereby the lens member IM3 and the lens holder LH are positioned in the optical-axis direction. On the other hand, the optical surfaces or the peripheral surfaces of the convex lens units PL2, PL3 abut on the apertures AP2, AP3, thereby attaining the positioning in an optical-axis orthogonal direction and the positioning around a Z-axis.